Degradation of ethylenediaminetetraacetic acid (EDTA) in aqueous solution by means of ozonolysis or ozonolysis combined with sonolysis was investigated for a variety of operating conditions. Synergistic effects can be observed when ozonolysis was combined with sonolysis because additional (OH)-O-center dot was produced. It was found that the degradation of EDTA in aqueous solution follows the pseudo-first-order reaction kinetics and the degradation rate depends on the initial concentration of EDTA, the temperature and the acidity of the aqueous medium. The main degradation products of EDTA, such as amino acid and nitrate were tentatively identified by using GC-MS and ion chromatogram techniques. (C) 2009 Elsevier B.V. All rights reserved.